package com.zhupanlin.sqlSession;

import com.zhupanlin.config.BoundSql;
import com.zhupanlin.pojo.Configuration;
import com.zhupanlin.pojo.MappedStatement;
import com.zhupanlin.utils.GenericTokenParser;
import com.zhupanlin.utils.ParameterMapping;
import com.zhupanlin.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * 描述信息：
 *
 * @author zhupanlin
 * @version 1.0
 * @date 2025/2/8 18:18
 */
public class SimpleExecutor implements Executor{
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        
        // 2. 获取 sql 语句
        String sql = mappedStatement.getSql();
        
        // 转换 sql 语句，将 #{} 转换成 ? ，还需要对 #{} 里面的值进行解析存储
        BoundSql boundSql = getBoundSql(sql);
        
        // 3. 获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        
        // 4. 设置参数
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        // 获取参数类型
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        /*if (parameterTypeClass == null) {
            throw new RuntimeException("不存在该类型:" + parameterType);
        }*/
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            // 允许访问私有属性
            declaredField.setAccessible(true);
            Object declaredFieldValue = declaredField.get(params[0]);
            
            preparedStatement.setObject(i + 1, declaredFieldValue);

        }
        // 5. 执行 sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultClass = getClassType(resultType);
        if (resultClass == null) {
            throw new RuntimeException("不存在该类型:" + resultType);
        }
        List<Object> results = new ArrayList<>();

        // 6. 封装返回结果集
        while (resultSet.next()) {
            Object result = resultClass.newInstance();
            // 元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段值
                Object value = resultSet.getObject(columnName);
                // 使用反射创建对象，并给值
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(result, value);
            }
            results.add(result);
        }


        return (List<E>) results;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对 #{} 的解析工作
     * 将 #{} 转换成 ?
     * 解析出 #{} 里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        // 标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        
        // 解析出来的 sql
        String parseSql = genericTokenParser.parse(sql);
        // #{} 里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        
        return boundSql;
    }
}